Insectivorous Plants eBook

I have now given a brief recapitulation of the chief
points observed by me, with respect to the structure,
movements, constitution, and habits of Drosera rotundifolia;
and we see how little has been made out in comparison
with what remains unexplained and unknown. [page 278]

CHAPTER XII.

I examined six other species of Drosera, some
of them inhabitants of distant countries, chiefly
for the sake of ascertaining whether they caught insects.
This seemed the more necessary as the leaves of some
of the species differ to an extraordinary degree in
shape from the rounded ones of Drosera rotundifolia.
In functional powers, however, they differ very little.

[Drosera anglica (Hudson).*—­The leaves
of this species, which was sent to me from Ireland,
are much elongated, and gradually widen from the footstalk
to the bluntly pointed apex. They stand almost
erect, and their blades sometimes exceed 1 inch in
length, whilst their breadth is only the 1/5 of an
inch. The glands of all the tentacles have the
same structure, so that the extreme marginal ones
do not differ from the others, as in the case of Drosera
rotundifolia. When they are irritated by being
roughly touched, or by the pressure of minute inorganic
particles, or by contact with animal matter, or by
the absorption of carbonate of ammonia, the tentacles
become inflected; the basal portion being the chief
seat of movement. Cutting or pricking the blade
of the leaf did not excite any movement. They
frequently capture insects, and the glands of the
inflected tentacles pour forth much acid secretion.
Bits of roast meat were placed on some glands, and
the tentacles began to move in 1 m. or

* Mrs. Treat has given an excellent account in ’The
American Naturalist,’ December 1873, p. 705,
of Drosera longifolia (which is a synonym in part
of Drosera anglica), of Drosera rotundifolia and filiformis.
[page 279]

1 m. 30 s.; and in 1 hr. 10 m. reached the centre.
Two bits of boiled cork, one of boiled thread, and
two of coal-cinders taken from the fire, were placed,
by the aid of an instrument which had been immersed
in boiling water, on five glands; these superfluous
precautions having been taken on account of M. Ziegler’s
statements. One of the particles of cinder caused
some inflection in 8 hrs. 45 m., as did after 23 hrs.
the other particle of cinder, the bit of thread, and
both bits of cork. Three glands were touched
half a dozen times with a needle; one of the tentacles
became well inflected in 17 m., and re-expanded after
24 hrs.; the two others never moved. The homogeneous
fluid within the cells of the tentacles undergoes
aggregation after these have become inflected; especially
if given a solution of carbonate of ammonia; and I
observed the usual movements in the masses of protoplasm.
In one case, aggregation ensued in 1 hr. 10 m. after
a tentacle had carried a bit of meat to the centre.
From these facts it is clear that the tentacles of
Drosera anglica behave like those of Drosera rotundifolia.